The Thorns selected North Carolina's Amber Brooks (22) with their third pick (No. 24 overall) in the NWSL college draft on Friday.The Associated Press

Kathryn Williamson thought her friends were playing a not-very-nice joke on her.

That was Williamson's initial reaction when her fellow University of Florida teammates told her that she had been drafted by the Portland Thorns Friday morning.

"They were on computers and I was on Twitter on my phone. I guess their computer was faster than my phone, because they started screaming and said I got drafted," Williamson said. "I thought they were joking, because it hadn't come up on my phone yet. I'm like, 'That is a really mean joke.' "

The friends weren't joking. Williamson was the first (eighth overall) of four players selected by the Thorns during the National Women's Soccer League's college draft Friday morning. The eight-team league selected players during four rounds and Williamson was the Thorns' first-ever collegiate draft pick.

"I was so excited when I found out that Portland had chosen me," Williamson said. "It is such an amazing feeling."

The Thorns also selected forward Nicolette Radovcic from the University of Central Florida in the second round (16th overall), midfielder Amber Brooks from North Carolina in the third round (24th overall) and goalkeeper Roxanne Barker from Pepperdine in the fourth round (32nd overall).

Williamson, a center back, was an All-American selection in 2010 and 2011 and a member of the Gators' team that reached the Round of 16 in the 2012 NCAA Tournament.

"We felt like we really needed someone who could play both center back and outside back," Portland coach Cindy Parlow Cone said. "In my opinion, Kat is a top defender in college right now. She's very good technically and has tremendous speed and she fits in with the way we want to play - building the ball out of the back."

Williamson said she has played primarily at center back, but quickly added that she does possess experience playing at outside back in college.

"Wherever I can get on the field, I'm ready to play that position," Williamson said.

Williamson's Gators eliminated Radovcic's Knights in a NCAA Tournament second-round game in 2012. Radovcic led the Knights the past two seasons and including 12 goals in 24 games in 2012. She finished her career with 30 goals and 16 assists.

Cone, an assistant coach at North Carolina before coming to Portland, is very familiar with Brooks. Brooks started all 23 games during the season, recording seven goals and six assists during the Tar Heels' run to the NCAA championship in 2012.

"She is a holding midfielder, but she can also play in the back," Cone said.

The team's roster is limited to 20 players and with some many different scenarios surfacing during the season, Cone selected players who are capable of playing different positions if needed.

"With national team call-ups, we're going to have to have players who can play a couple of different positions," Cone said.

Cone said she'll look to the supplemental draft in February and free agent signings to fill out the roster. The team is expected to begin training camp in mid-March.